Electromagnetic pump and energizing means therefor



Dec. 22, 1964 M. E. LOVELL 3,162,134

ELECTROMAGNETIC PUMP AND ENERGIZING MEANS THEREFOR Filed Nov. 24, 1961 3 Sheets-Sheet 1 L 43 F -12- J 74 f I Q 76 INVENTOR. 24 M42! 5 [ow-LA M. E. LOVELL Dec. 22, 1964 ELECTROMAGNETIC PUMP AND ENERGIZING MEANS THEREFOR 3 Sheets-Sheet 2 Filed Nov. 24, 1961 ffi' INVENTOR.

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M. E. LOVELL Dec. 22, 1964 ELECTROMAGNETIC PUMP AND ENERGIZING MEANS THEREFOR Filed Nov. 24, 1961 United States Patent 0 3,162,134 nrneraoaraennrre PUMP arsn MEANS THEREFQR Mark E. Loveil, sees dramas thrive, Sherman Oaks, Caiir. Filed Nov. 2 5, 1962i, Ser. No. 154,417 8 (Cl. NE -53) This invention relates generally to fluid pumps and has as it general object to provide an improved electromagnetically actuated piston pump or compressor and an energizing circuit therefor.

Another object of the invention is to provide an improved electromagnetically actuated piston pump which has a high operating efiiciency and a long operating life.

Yet another object of the invention is to provide an improved electromagnetically actuated piston pump which is completely leakproof and embodies no packing glands or shaft seals so as to be uniquely adapted to applications wherein leakage of the fiuid being pumped must be avoided, as in the case of corrosive, explosive, and high temperature fluids, as wall as to applications wherein contamination of the fluid being pumped must be avoided for sanitary or other reasons.

A further object of the invention is to provide an improved electrontiagnetically actuated piston pump in which two windings are alternately energized to reciprocate the pump piston, and an energizing circuit for the pump which is devoid of any moving electrical contacts or other points of arcing during alternate energizing and deenergizing of the pump windings, which is adjustable to vary the pumping rate and/or the discharge pressure of the pump, and which can be manually controlled, from a remote location, if desired, to allow metering of a known volume of liquid into a system. I

' A still further object of the invention is to provide an electromagnetically actuated piston pump of the character described and an energizing circuit therefor which can be powered from an A.C. source or a DC. source, such as batteries, so as to be adapted for use in installations having only an A.C. power supply or a dual power supply, such as hospitals and ships, as well as in mobile installations having only a DC. power supply, such as trucks and trains. The DC. power supply can be conditioned for emergency stand-by operation to assume energizing of the pump automatically. in response to failure of the A.C. supply.

Yet a further object of the invention is to provide an electromagnetically actuated pump which is compact, may be single-acting or double-acting, can be readily cleaned, and possesses various other unique features of construction and operation whereby the pump is ideally suited to its intended purposes.

Briefly, the objects of the invention are achieved by providing a pump equipped with a nonmagnetically permeable cylinder, at magneticallypermeable piston in the cylinder, and an electromagnetic field structure on the outside of the cylinder. This field structure includes three poles located at the center and ends, respectively, of the cylinder and two windings to be alternately energized for creating electromagnetic fields between the two end poles and the center pole alternately. One field moves the piston in one direction in the cylinder and the other field moves the piston in the opposite direction.

The pump windings are alternately energized, to reciprocate the piston in the cylinder, by an electrical circuit utilizing silicon control rectifiers in series with the pump windings and an oscillator for triggering these rectifiers in such a way as to allow current flow through the windings alternately. This circuit has no moving contacts or other points at which arcing might occur during alternate energizing and denergizing of the pump windings.

The output frequency of the oscillator can be.

varied to vary the pump speed, and the current ilow through the windings can be adjusted tovary the discharge pressure. Suitable check or electromagnetic valves are used to efiect a flow of fluid from the pump inlet to the pump outlet during operation of the pump.

The energizing circuit has provision for operation of the pump from either an A.C. power supply or a DC or battery power supply and can be conditioned for operation of the pump from either supply. The circuit embodies an A.C. power failure relay which is adapted to effect operation of the pump by the battery supply automatically in response to failure of the A.C. supply. Means are provided in the circuit for manual triggering of the pump, and the circuit has jacks for connection to a remote control unit whereby the pump can be manually controlled from a remote location.

One illustrative embodiment of the present pump is double-acting. Another illustrative embodiment is singleacting. According to the invention, the pump cylinder may be detachable from the field structure to permit the latter to be used with diiferent cylinders or the cylinder with different field structures. One illustrative embodiment utilizes liquid coolant passages and is otherwise uniquely designed for high temperature operation.

The invention will be better understood from the following detailed description thereof, taken in connection with the attached drawings, wherein:

FIG. 1 illustrates a double-acting electromagnetically actuated pump according to the invention;

PEG. 2 is an enlarged section taken along line 2-2 on FIG. 1;

FIG. 3 illustrates a singleacting, liquid cooled, electromagnetically actuated pump according to the invention;

FIG. 4 is a section taken along line 4-4 on FIG. 3;

FIG. 5 diagrammatically illustrates an oscillator circuit for alternately energizing the windings of the pumps shown in FIGS. 1 and 3; and

FIG. 6 diagrammatically illustrates an alternative electromagnetic valve arrangement for the pump.

Pump 19 illustrated in FIGS. 1 and 2 of these drawings comprises a magnetically permeable cylindrical housing 12. Closing the ends of this housing are magnetically permeable discs or end plates 14. Within, and midway between the ends of the housing 12, is a center, magnetically permeable disc or plate 16. Plates 14 and lid have central, coaxial bores 18, 2t and 22. Extending from one end of the pump to the other and through these coaxial bores is a nonmagnetically permeable sleeve 24 which forms the cylinder of the pump. Cylinder 24 has a close sliding fit in the bores so that the cylinder may be removed for repair or replacement. End plates 14 are secured to the housing 12 by bolts 26. Center plate 16 may be formed integrally with the housing 12., as shown, or it may be a separate piece which is press fitted or otherwise fixed in the housing or shell 12.

Encircling the left-hand end of the pump cylinder 24, within the annular space between the left-hand end plate 1 and the center plate 16, is a first electromagnetic coil or winding 28. Encircling the right-hand end of the cylinder, within the annular space between the righthand end plate 14 and center plate 16, is a second electromagnetic coil or winding 30. These windings are preferably wound on annular forms or spools 32 so that the windings can be easily inserted into and removed from the pump by removing the end plates 14.

. Closely but removably fitted in the ends of the pump cylinder 24; are magnetically ermeable plugs 34. 0- rings 35 provide a fluid-tight seal between the cylinder and the plugs. Plugs 34 are formed wtih radial flanges or shoulders 33 which position them axially in the pump cylinder.

Plugs 3d are formed with outer, axial extensions til which are cylindrically recessed at their ends to seat transverse fluid conduits 42. The plug extensions 4% and conduits 4 are joined, as by welding. Extending axially through the plugs 34 are fluid passages 44 which open at one end to the adjacent end of the pump cylinder 24 and at the other end into the adjacent fluid conduit 42. Welded to opposite sides of each fluid conduit 42 are slotted flanges 45. A pair of toggle bolts 46 are hinged to each end plate 14 and are received in the slots of the flanges 45. Encircling the outer ends of these bolts, between the flanges 4-5 and nuts 45 on the outer ends of the bolts; are compression springs 5d. Springs 50, therefore, yieldably retain the plugs 34 in position in the ends of the pump cylinder 24.

Slidably received within the pump cylinder 24, for reciprocation between the plugs 3 is a magnetically permeable piston 52. The inner ends of the plugs 34 are tapered, as shown, and the ends of the piston 52 are formed with tapered recesses 54 which complement the tapered ends of the plugs, for reasons to be presently discussed.

Threaded in and extending axially from each end of the piston 52 is a stem 56. Stems as extend through central bores 58 in the plugs and into the fluid conduits 42. Compression springs 69, aligned with the stems 56, are contained within-spring holders 62 threaded in the fluid conduits 42. During left-hand movement of the piston 52 in the cylinder 24, the left-hand stem 56 engages and compresses the left-hand spring (it). During right hand travel of the piston 52 in the pump cylinder 2d, the righthand stem 56 engages and compresses the right-hand spring 61 The function of these springs will be described shortly.

The shell 12, end plates 14, center plate 16, and windings 28 and 30 form an electromagnetic field structure on the outside of the pump cylinder 24. The inner edge portions of the plates 14 and 16, about their respective bores 13, 2t), and 22, form the poles P P and P of this magnetic field structure. Poles P and P are located at the ends, respectively, of the pump cylinder 24 and in close proximity to (in actual contact with) the pump cylinder. The third pole P is located at the center of and in close proximity to (in actual contact with) the center of the pump cylinder.

it is evident that when the left-hand winding 28 is energized, a magnetic field is created between the center pole P and the pole P at the left-hand end of the pump cylinder 24. Recalling that the plugs 34 and piston 52 are constructed of magnetically permeable material, and observing that the left-hand pole P is closely adjacent the lefthand plug 34- and the center pole P is closely adjacent the piston 52, it is evident that magnetic lines of force of the magnetic field created by energization of the left-hand winding 28 extend between the left-hand plug and the piston and across the air gap A between these parts. An electromagnetic force is thereby created on the piston 52 which acts to move the latter in a direction to reduce the air gap A. When the winding 28 is energized, therefore, piston 52 is moved to the left in FIG. 2 by the action of the electromagnetic field. Similarly, when the right-hand winding 3% is energized, magnetic lines of force extend between the right-hand plug 34 and the piston 52 and across the aim gap A between these parts. An electromagnetic force then acts on the piston 52 to move the latter in a direction to reduce the air gap A. Accordingly, when the winding 32d is energized, the pump piston 52 is moved to the right in FIG. 2. From this description, it is evident that the piston 52 may be reciprocated Within the pump cylinder 24 by alternate energizing of the pump windings 28 and 30. The inner ends of the plugs 34 and the ends of the piston 52 are tapered, as described earlier, in accordance with conventional practice for the purpose of reducing the air gap between these parts and, therefore, increasing the electromagnetic force on the piston, while maintaining a given overall piston travel.

Cir

It is evident that when either of the windings 28 or 3% is energized, the electromagnetic force on the piston increases rapidly as the air gap between the piston and the corresponding plug 34- decrcases. This rapidly increasing force on the piston at the ends of its travel in the pump cylinder produces periodic pressure peaks in the pump output, which peaks may be undesirable. Springs 6%? are provided to minimize these peaks. Thus, the piston stems 56 are proportioned so that they engage their respective springs 69 at some position in the corresponding direction of travel of the piston. During the remaining part of the piston travel, the springs tit) are compressed by the piston stems. When the magnetic field of the pump is reversed, the compressed spring exerts a force on the piston in the same direction as the elec tromagnetic force developed by the reversed magnetic field. Thus, during the terminal portion of each stroke of the piston 52, one or the other of the pump springs 60 absorbs a portion of the energy of the electromagnetic field which is currently moving the piston and, upon reversal of the pump field to reverse the direction of travel of the piston, delivers this energy to the piston in a direction to aid the reversed field. Springs 69, therefore, act to equalize the output pressure of the pump.

In FIG. 1, the inlet of the pump is designated by the numeral 64 and the output of the pump by the numeral 66. Inlet 64 connects to a T 6% from which extend two branch fluid lines 79 and '72. Branch line terminates in a flanged valve housing 74 which is bolted to the lower flanged end of the left-hand pump conduit 42. Branch line '74 terminates in a flanged valve housing 76 which is bolted to the lower flanged end of the right-hand pump conduit 42.

Similarly, pump outlet 66 connects to a T '78 from which extend two branch fluid lines 8i) and 82. Branch line 80 terminates in a flanged valve housing 34 which is bolted to the flanged upper end of the left-hand pump conduit 42. Branch line 82 terminates in a flanged valve housing 86 which is bolted to the upper flanged end of the right-hand pump conduit 42.

Contained within valve housings 7d, 76, 84, 36 are suitable check valves, not shown, which permit fluid flow in the direction indicated by the arrow on each valve housing.

From this description, it is evident that when pump winding 28 is energized to cause left-hand travel of the piston 52 in the pump cylinder 24, fluid is drawn into the right-hand end of the cylinder through check valve 76, the right-hand pump conduit 42, and the fluid passages 44 in the right-hand cylinder plug 34. Check valve 86 is closed. Simultaneously, fluid is expelled from the left-hand end of the cylinder 24 through the fluid passages 44 in the lefthand cylinder plug 34, the left-hand pump conduit '42, and check valve 8 Check valve 74 is closed.

Similarly, when pump winding 30 is energized to cause right-hand travel of the piston 52 in the pump cylinder 24, fluid is drawn into the left-hand end of the cylinder through check valve '74, the left-hand pump conduit 42, and the fluid passages 44 in the left-hand cylinder plug 34. Simultaneously, fluid is expelled from the right-hand end of the cylinder 24 through the fluid passages 44 in the right-hand cylinder plug 34, the right-hand pump conduit 42, and the check valve s-s. Check valves 76 and 84 are now closed.

Thus, during each right-hand and left-hand stroke of the piston 52, fluid is pumped from the pump inlet 64 to the pump outlet 66.

Reference is now made to FIG. 5 illustrating the circuit 88 for alternately energizing the pump windings 23 and 30. Circuit 88 comprises a transformer 96 and an A.C. power failure-relay 92. The primary winding 94hr of the transformer 99 and the coil 92a of the relay 92 are connected with a pair of AC. power input terminals 94 through a line switch 96. Also connected to the A.C. input terminals 94, through a stand-by switch 93, is an autotransformer ltltl. The secondary winding iitlb of the transformer ht energizes a full wave bridge rectifier ltiZ. The output of this rectifier is connected to a conventional shunt voltage regulator 104 consisting of a resistor 1640, a Ze'ner diode lltldb, and a capacitor ltldc. The shunt voltage regulator the operates in the welldrnown to develop a constant DC. output which is fed to a conventional unijunction transistor oscillator 1%. This oscillator generates a pulse output voltage, the pulse rate of which is determined by the RC constant of a resistor idea, a potentiometer ltleb, and a capacitor lilac in the oscillator circuit. Adjustment of the potentiometer ltldb, then, varies the pulse rate of the oscillator.

The pulsed output of the oscillator 1% is impressed across the primary winding 108a of a pulse transformer M8. This transformer has two secondary windings lttfib and ltltlc which are connected, through manual pulse switches lllltl and H2 and blocking diodes ill i and lid, to the gate-cathode circuits of two silicon control rectifiers 113 and 1%.

The autotransformer 1M supplies variable A.C. power to the primary winding 12211 of a transformer 122, the secondary winding 12217 of which is connected to a full wave bridge rectifier 124. A capacitor 126 is connected across the output of this rectifier and provides a zero source impedance to the reactive power fiowing in the circuit. Pumpwindings 28 and 3%) have a common connection to a lead 128 which connects to the negative output terminal of the rectifier 124. The positive output terminal of the rectifier 124 is connected through a lead 12! to the common heat sink (not shown) of the silicon control rectifiers 118 and 120 and to a pair of bypass diodes 13! and 132.

When a voltage pulse is applied to the gates of the silicon control rectifiers 113 and 120 from the oscillator Th5 through the pulse transformer 16%, one of the rectifiers will always start to conduct at a lower gate voltage than the other due to the slight difference in the characteristics between any two silicon rectifiers. Let us assume that silicon control rectifier 11th starts to conduct first. Conduction of the silicon control rectifier lltl retains the silicon control rectifier lit; in its nonconducting state and conducts current from lead l2) through the pump winding 23 to the lead lZfi. Due to transformer action, twice the applied voltage appears across the two outside terminals of the pump windings Z3 and 30. This voltage charges a commutating capacitor E34, connected across the two outside terminals of the pump windings, to twice the line voltage. When the next voltage pulse appears at the gates of the silicon control rectifiers 118 and 12%, rectifier illtl conducts and the charged commutating capacitor 134 places a back bias voltage on the silicon control rectifier 11$ so that the latter is returned to its nonconducting state. Silicon control rectifier 12% now conducts a current through pump winding Stl, and the commutating capacitor 154 is charged in the opposite direction. During the next voltage pulse from the oscillator ms, the commutating capacitor 134- places a back bias voltage on the silicon control rectifier lit? to return the latter to its nonconducting state and silicon control rectifier M8 again conducts. Thus, the output pulses from the oscillator 1% cause alternate energizing of the pump windings Z8 and 3t? to reciprocate the pump piston in the pump cylinder.

Taps are brought out of the pump windings 23 and 3A? and connected to the bypass diodes 13d and 1321 to aid in discharging the windings and thereby permit the use of lower voltage ratings for the silicon control rectificrs lid and 120. An RC filter network 136, consisting of a capacitor 156a and a resistor 136b, is connected across the anode and cathode of each silicon control rectifier to suppress transient switching voltages which could damage the rectifiers. A switch 138 and a capacitor 1% are con nected in shunt with the commutating capacitor 1% to permit the effective commutating capacitance, and, theretore, the silicon control rectifier hold-off time requirement, to be varied as the frequency is varied.

in lead 142, connecting one output terminal of the shunt voltage regulator 1% to the oscillator 1%, is a jack 144. This jack is adapted to receive the plug on the end of a cable leading to a remote switch unit (not shown). When the plug is inserted in the jack 144, the latter is opened to break the energizing circuit for the oscillator res so that the latter remains inoperative until the remote switch unit is closed. In this way, the operation of the pump can be controlled from a remote location.

indicated at are is asecond jack which is connected in shunt with the oscillator pulse repetition rate potentiometer snob. This jack is adapted to receive the plug on the end of a cable leading to a remote potentiometer unit (not shown). When the plug is inserted into the jack 1 36, the oscillator potentiometer ltidb is removed from the oscillator circuit and the potentiometer in the remote potentiometer unit is inserted in the circuit so that the pulse repetition rate or" the oscillator, and, therefore, the pumping rate of the pump, may be controlled from a remote location.

Numeral 14$ denotes a manual-automatic switch which, when closed, shorts out the pulse repetition rate potentiometer lltldb of the oscillator 1%. The values of the oscillator resistor lfida and oscillator capacitor ltldc are such that when the potentiometer lltlob is thus shorted out, the pulse rate of the oscillator is extremely high. The mass of the pump piston is such that it cannot respond to this high frequencyand, therefore, locks into a stationary position determined by which of the pump windings 28 or 3th is currently energized when the manualautomatic switch 14$ is closed. The manual pump switches llltl and 112 may now be operated, as follows: When switch is opened, it momentarily removes the gate signal from silicon control rectifier 118 and deenergizes the associated pump winding 28 so that the pump plunger moves in one direction. The piston now locks into a stationary position in the pump winding 30. When the manual pulse switch 112 is depressed, the gate signal is removed from the silicon control rectifier 126 which deenergizes the pump winding 30 resulting in movement of the piston into the pump winding 28. The pump piston then remains stationary in this position until the switch 1.14) is again depressed to repeat the cycle.

Batteries 15th and 152 are provided for emergency stand-by operation in the event of failure of the A.C. power supply to the A.C. input terminals 94 of the circuit. In the event of such failure, the coil 92a of the A.C. power failure relay 92 is deenergized and its switch contacts hZb and 92c close. connects the battery 15th to the oscillator 1% which is thereby energized in the same manner as it was energized by the shunt voltage regulator 1G4. Closure of relay contacts 92c connects the second battery 152 into the circuits of the silicon control rectifiers 118 and 12%. Thus, when the A.C. power relay 92 is deenergized upon failure of the A.C. power supply, the batteries 15% and 152 are automatically connected into the circuit to continue operation of the pump. Switches 156 and 158 are connected in shunt with the A.C. power failure relay contacts 2b andQZc .to permit selective operation of the circuit from either an A.C. power source or the batteries 15% and 152 as well as to allow charging of the batteries from the rectifier i2 5 while the unit is operating from an A.C. supply. An emergency stand-by switch lad is connected in the battery leads, as shown. Stand-by switch 98, emergency stand-by switch 164i, and the charging switches 15%, 158 permit charging of the batteries 15d, l52 from the rectifier 1124 while the pump 'is inoperative. Terminals 162 are provided to ailord a DC. voltage check point.

The single-acting pump in- FIG. 3 comprisesa nonmagnetically permeable cylinder 2th) closed at its ends by magnetically permeable plugs 2tl2, each having a central fluid passage Z04 Communicating with the left-hand Closure of relay contacts 9211 s ears s 7 plug passage 204 is a fluid inlet line 206 and with the right-hand plug passage 204 a fluid discharge line 298.

Reciprocable within the cylinder between these plugs is a magnetically permeable piston 210. Piston 214 has a central through passage 212 in which is a check valve 214.

During left-hand travel of the piston 21% in the cylinder 200, fluid in the left-hand end of the cylinder fiows through the piston passage 212 and past the check valve 214, which unseats during flow in this direction of piston travel, into the right-hand end of the cylinder. During subsequent right-hand travel of the piston, the check valve 214 closes so that fluid is expelled from the right-hand end of the pump cylinder through the discharge line 2'08. Simultaneously, fluid is drawn into the left-hand end of the cylinder through the inlet line 2%.

The electromagnetic field structure 216 of the pump comprises three magnetically permeable bars 218, 22%, and 222 located at the ends and center, respectively, of the pump cylinder 200. These bars are attached to a magnetically permeable crossbar 224. Pump winding 226 is mounted on the left-hand bar 218 and the other pump winding 228 is mounted on the right-hand bar 222.

The pump cylinder 200 could be permanently mounted in the magnetic field bars 2.18, 229, 222 by press fitting the cylinder in aligned bores in the bars. Preferably, however, the upper ends of the field bars terminate approximately at the center line of the cylinder and are cylindrically relieved to seat the cylinder, as shown. Magnetically permeable caps 23S), hinged to the upper ends of the field bars 218, 22%, and 222, fit over the cylinder and are secured to the field bars by releasable locks 232. Locks 232 can be released to permit hinging of the caps 230 to a position wherein the cylinder 2% can be removed from the magnetic field structure 216.

One cylinder and piston assembly can thereby be replaced by another. In this way, pump cylinders of various displacements (the pump displacement may be varied by varying the length of the cylinder plugs 292 to change the piston stroke and/or varying the diameter of the cylinder bore) may be installed on the field structure. Also, the field structure may be used with cylinder and piston assemblies in several fiuid systems containing different fluids. While the hinged caps 230 have been disclosed for locking the pump cylinder 2% to the magnetic field bars 218, 22th, and 222, it has been found that such caps may be dispensed with and the magnetic attraction between the parts relied on to hold the cylinder firmly in position on the field structure.

In operation, the pump windings 226 and 228 are alternately energized by the circuit of FIG. 5, for example. The upper ends of the field bars 218, 22%, 222 form poles P P P located at the center and ends, respectively, of the cylinder. When winding 226 is energized, an electromagnetic field is created between the center pole P and the left-hand pole P magnetic lines of force of which extend between the left-hand cylinder plug 202 and the piston 210, as in the previous form of the invention. The piston is thereby moved to the left in the cylinder 200 by the field. Similarly, when pump winding 223 is energized, an electromagnetic field is created between the center pole P and the-right-hand pole P and the piston is moved to the right in the cylinder. Thus, when the windings are alternately energized by the circuit of FIG. 5, fluid is pumped from the pump inlet line 2% to the pump outlet line 208.

' One advantage of the pump configuration of FIG. 3 is that the magnetic field bars 218, 220, 222 may be made quite long and the pump windings 226 and 228 may be located adjacent the lower ends of the bars so that a considerable spacing will exist between the pump cylinder 200 and the pump windings. In this way, the windings are effectively shielded from the heat radiated and conducted from the cylinderwhen pumping high temperature fluids, such as molten metal. Such high temperature fluids, of course, will require the pump parts to be made of a metal capable of withstanding the high temperatures involved. The maximum operating temperature of the pump is obviously governed by the Curie point of the material used in the electromagnetic circuit of the pump.

The present pump may be made to operate effectively up to 500 F. without any cooling or shielding in addition to that achieved by making the magnetic field bars quite long. If necessary, the operating temperature of the pump can be increased to the maximum by providing the field structure 216 with passages 234 through which a suitable liquid coolant may be circulated for cooling the pump windings 226, 228 and other parts of the field structure.

The pump diagrammatically illustrated in FIG. 6 comprises a pump lfia, proper, generally like that illustrated in FIG. 1. In FIG. 6, however, the check valves 74, 76, 8 5, 36 of the pump of FIG. 1 are replaced by springclosed, electromagnetically opened solenoid valves 74a, 76a, 84a, 85a. The windings of valves 74:: and 86a are connected in electrical circuit with pump winding 30a so as to be electromagnetically opened when this winding is energized. The valves are spring loaded to close when the winding is deenergized. Similarly, the windings of valves Ida and 84:; are connected in electrical circuit with pump winding 28a so as to be electromagnetically opened when the latter winding is energized. The valves are spring loaded to close upon deenergizing of the wind- In this form of the invention, the pump valves are electromagnetically operated in synchronism with move ment of the pump piston (not shown) in its cylinder (not shown) to effect flow of the fluid being pumped from the pump inlet to the pump outlet.

It is obvious that since the various pumps of this invention are devoid of shaft seals and may be completely hermetically sealed, they are uniquely adapted to pumping molten metals as well as corrosive or noncorrosive materials without fear of leakage, seal deterioration, or contamination by exernal atmosphere or seal or bearing lubricant.

Clearly, then, the invention is fully capable of attaining the objects and advantages preliminarily set forth.

What is claimed is:

1. In combination, a nonmagnetically permeable cylinder; an electromagnetic field structure on the outside of said cylinder including three poles located at the center and ends, respectively, of said cylinder, a first winding to be energized for creating a first electromagnetic field between said center pole and one end pole, and a second winding to be energized for creating a second electromagnetic field between said centcr pole and the other end pole; a magnetically permeable plunger reciprocable in said cylinder between said end poles, said center pole being disposed in close proximity to said plunger, whereby when said first winding is energized, magnetic lines of force of said first field extend between said one end pole and said plunger and the latter is moved toward said one end pole, and when said second winding is energized, magnetic lines of force of said second field extend between said other end pole and said plunger and the latter is moved toward said other end pole; and an energizing circuit for said windings comprising silicon control rectifiers in circuit with said windngs, respec tively, means to impress a voltage across said windings and rectifiers, an electrical oscillator for generating periodic electrical impuises, and circuit means for applying the output of said oscillator to the gates of said rectifiers, whereby the latter are periodically triggered to allow current flow through said windings, including a commutating capacitor connected across said windings for causing said rectifiers'to be triggered alternately by said impulses.

2. The subject matter of claim 1, wherein said oscillator includes means for varying the frequency of said im-; pulses whereby to vary the rate of reciprocation of said plunger in said cylinder.

3. The subject matter of claim 1, wherein said oscillator includes a potentiometer for varying the frequency of said impulses, whereby to vary the rate of reciprocation of said plunger in said cylinder, and means for connecting a remote control potentiometer in shunt with said first-mentioned potentiometer and electrically isolating the latter from said circuit.

4. The subject matter of claim 1, including means for connecting a remote control switch unit in circuit with said oscillator for selectively activating and deactivating the latter from a remote position.

5. The subject matter of claim 1, wherein said circuit includes further a pair of terminals for connection to an AC. power source, a first rectifier in circuit with said terminals and said oscillator, a second rectifier in circuit with said terminals and said silicon control rectifiers, battery means, circuit means connecting said battery means and said oscillator and silicon control rectifiers in parallel with said rectifier means, and relay means for controlling current flow in said circuit means in response to the current flow to said terminals.

6. The subject matter of claim 1, wherein said circuit means includes further means for selectively causing said oscillator to supply high frequency impulses to said silicon control rectifiers, whereby said plunger remains stationary in said cylinder, and switch means for selectively deenergizing each winding to effect manual control of said plunger.

7. A fluid pump comprising a nonmagnetically permeable cylinder; an electromagnetic field structure on the outside of said cylinder including three poles located at the center and ends, respectively, of said cylinder, a first winding to be energized for creating a first electromagnetic field between said center pole and one end pole, and a second winding to be energized for creating a second electromagnetic field between said center pole and the other end pole; a magnetically permeable piston reciprocable in said cylinder between said end poles, said center pole being disposed in close proximity to said piston, whereby when said first winding is energized, magnetic lines of force of said first field extend between said one end pole and said piston and the latter is moved toward said one end pole, and when said second winding is energized, magnetic lines of force of said second field extend between said other end pole and said piston and the latter is moved toward said other end pole, said pump having a fluid inlet and fiuid outlet; valve means between said inlet and outlet for effecting flow of fluid from the inlet to the outlet during reciprocation of said piston in said cylinder by alternate energizing of said windings; and an energizing circuit for said windings comprising silicon control rectifiers in circuit with said windings, respectively, means to impress a voltage across said windings and rectifiers, a semiconductor oscillator for generating periodic electrical impulses, and circuit means for applying the output of said oscillator to said rectifiers, whereby the latter are periodically triggered to allow current flow through said windings, including a commutating capacitor connected across said rectifiers for causing said rectifiers to be triggered alternately by said impulses.

8. A fluid pump comprising a nonmagnetically permeable cylinder; an electromagnetic field structure on the outside of said cylinder including three poles located at the center and ends, respectively, of said cylinder, at first winding to be energized for creating a first electromagnetic field between said center pole and one end pole, and a second winding to be energized for creating a second electromagnetic field between said center pole and the other end pole; a magnetically permeable piston reciprocable in said cylinder between said end poles, said center pole being disposed in close proximity to said piston, whereby when said first winding is energized, magnetic lines of force of said first field extend between said one end pole and said piston and the latter is moved toward said one end pole, and when said second winding is energized, magnetic lines of force of said second field extend between said other end pole and said piston and the latter is moved toward said other end pole, said pump having a fluid inlet and a fluid outlet; valve means between said inlet and outlet for efiecting flow of fiuid from the inlet to the outlet during reciprocation of said piston in said cylinder by alternate energizing of said windings; and an energizing circuit for said windings comprising silicon control rectifiers in circuit with said windings, respectively, means to impress a voltage across said wind ings and rectifiers, a unijunction transistor oscillator for generating periodic electrical impulses, and circuit means for applying the output of said oscillator to said rectifiers, whereby the latter are periodically triggered to allow current fiow through said windings, including a commutating capacitor connected across said rectifiers for causing said rectifiers to be triggered alternately by said impulses.

References'Cited in the file of this patent UNITED STATES PATENTS 461,295 Van Depoele Oct. 13, 1891 1,684,468 Brown Sept. 18, 1928 2,686,280 Strong et al Aug. 10, 1954 2,688,930 De Moss Sept. 14, 1954 2,690,128 Basilewsky Sept. 28, 1954 2,713,311 vi hite luly 19, 1955 2,761,392 Parker M Sept. 4, 1956 2,833,220 Robinson et al May 6, 1958 2,862,450 McDonnell Dec. 2, 1958 

1. IN COMBINATION, A NONMAGNETICALLY PERMEABLE CYLINDER; AN ELECTROMAGNETIC FIELD STRUCTURE ON THE OUTSIDE OF SAID CYLINDER INCLUDING THREE POLES LOCATED AT THE CENTER AND ENDS, RESPECTIVELY, OF SAID CYLINDER, A FIRST WINDING TO BE ENERGIZED FOR CREATING A FIRST ELECTROMAGNETIC FIELD BETWEEN SAID CENTER POLE AND ONE END POLE, AND A SECOND WINDING TO BE ENERGIZED FOR CREATING A SECOND ELECTROMAGNETIC FIELD BETWEEN SAID CENTER POLE AND THE OTHER END POLE; A MAGNETICALLY PERMEABLE PLUNGER RECIPROCABLE IN SAID CYLINDER BETWEEN SAID END POLES, SAID CENTER POLE BEING DISPOSED IN CLOSE PROXIMITY TO SAID PLUNGER, WHEREBY WHEN SAID FIRST WINDING IS ENERGIZED, MAGNETIC LINES OF FORCE OF SAID FIRST FIELD EXTEND BETWEEN SAID ONE END POLE AND SAID PLUNGER AND THE LATTER IS MOVED TOWARD SAID ONE END POLE, AND WHEN SAID SECOND WINDING IS ENERGIZED, MAGNETIC LINES OF FORCE OF SAID SECOND FIELD EXTEND BETWEEN SAID OTHER END POLE AND SAID PLUNGER AND THE LATTER IS MOVED TOWARD SAID OTHER END POLE; AND AN ENERGIZING CIRCUIT FOR SAID WINDINGS COMPRISING SILICON CONTROL RECTIFIERS IN CIRCUIT WITH SAID WINDINGS, RESPECTIVELY, MEANS TO IMPRESS A VOLTAGE ACROSS SAID WINDINGS AND RECTIFIERS, AN ELECTRICAL OSCILLATOR FOR GENERATING PERIODIC ELECTRICAL IMPULSES, AND CIRCUIT MEANS FOR APPLYING THE OUTPUT OF SAID OSCILLATOR TO THE GATES OF SAID RECTIFIERS, WHEREBY THE LATTER ARE PERIODICALLY TRIGGERED TO ALLOW CURRENT FLOW THROUGH SAID WINDINGS, INCLUDING A COMMUTATING CAPACITOR CONNECTED ACROSS SAID WINDINGS FOR CAUSING SAID RECTIFIERS TO BE TRIGGERED ALTERNATELY BY SAID IMPULSES. 